This invention relates to a spatula-shaped light pen for controlling an image displayed on a CRT (cathode ray tube) screen.
Light pens have previously been used to control an image displayed on a CRT screen. However, for instance, in the case where the NTSC system is employed and an image is displayed on the CRT screen with a refresh time of about 1/60 second, the conventional light pen can read the coordinates of only one position in one field time (about 1/60 second).
Therefore, the conventional light pen is disadvantageous when the light pen is required to control a region. If it is assumed that the region consists of n points, it takes n.times.1/60 seconds for the light pen to control the region, because n points must be controlled with the light pen one after another.